Abstract
X-RAY measurements and limits on the Coma and Virgo clusters of galaxies have been said to limit the mass of hot gas in them to 2% of the amount required for stabilization according to the virial theorem1. Such a conclusion is strongly dependent on the value of the Hubble constant H0. The linear diameter of the cluster D and the cluster mass M, estimated by the virial theorem, each vary as H0−1. Therefore, the density ρ has the dependence ρ∼H02. The predicted X-ray flux F from this gas is ∼ρM/R2, where R is the distance to the cluster. R varies as H0−1. We therefore have the relation Meekins et al.1 appear to have used the value H0 = 95 km s−1 Mpc−1 found by van den Bergh2, because they took R= 70 Mpc. If Abell's value3H0 = 47 is used, the predicted flux is reduced by a factor of 0.12. A reduction of H0 to a value as low as 20 is not inconceivable. Although clumpiness increases F/M2, the presence of helium as a mass fraction f reduces F for fixed M in the ratio (1–½f).
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Meekins, J. F., Fritz, G., Chubb, T. A., Friedman, H., and Henry, R. C., Nature, 231, 107 (1971).
van den Bergh, S., Bull. Amer. Astron. Soc., 2, 223 (1970).
Abell, G. O., and Eastmond, S., Bull. Amer. Astron. Soc., 2, 179 (1970). See also de Vaucouleurs, G., Ap. J., 159, 435 (1970).
Allen, C. W., Astrophysical Quantities, second ed., 100 (The Athlone Press, London, 1962). (A factor Hz−1 must be supplied in the units for j v .)
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NOERDLINGER, P. The Hubble Constant and X-rays from Galaxy Clusters. Nature 232, 393 (1971). https://doi.org/10.1038/232393a0
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DOI: https://doi.org/10.1038/232393a0
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